Chronotype and emotion processing: a pilot study testing timing of online cognitive bias modification training

Background Circadian rhythms influence cognitive performance which peaks in the morning for early chronotypes and evening for late chronotypes. It is unknown whether cognitive interventions are susceptible to such synchrony effects and could be optimised at certain times-of-day. Objective A pilot study testing whether the effectiveness of cognitive bias modification (CBM) for facial emotion processing was improved when delivered at a time-of-day that was synchronised to chronotype. Methods 173 healthy young adults (aged 18–25) with an early or late chronotype completed one online session of CBM training in either the morning (06:00 hours to 10:00 hours) or evening (18:00 hours to 22:00 hours). Findings Moderate evidence that participants learnt better (higher post-training balance point) when they completed CBM training in the synchronous (evening for late chronotypes, morning for early chronotypes) compared with asynchronous (morning for late chronotypes, evening for early chronotypes) condition, controlling for pre-training balance point, sleep quality and negative affect. There was also a group×condition interaction where late chronotypes learnt faster and more effectively in synchronous versus asynchronous conditions. Conclusions Preliminary evidence that synchrony effects apply to this psychological intervention. Tailoring the delivery timing of CBM training to chronotype may optimise its effectiveness. This may be particularly important for late chronotypes who were less able to adapt to non-optimal times-of-day, possibly because they experience more social jetlag. Clinical implications To consider delivery timing of CBM training when administering to early and late chronotypes. This may generalise to other psychological interventions and be relevant for online interventions where the timing can be flexible.


Supplementary Figure 1. Cognitive Bias Modification (CBM) training.
A) In the baseline assessment, participants viewed 15 faces morphed between happy and sad.They judged these expressions to determine their 'balance point' (example in top panel).The training session provided tailored feedback after each trial to shift their balance point and emotion perception (example in bottom panel).B) Example CBM session training block with feedback presented.The baseline blocks followed an identical procedure but without the feedback window.Figure adapted from previous paper (23).

Questionnaires
Reduced Morningness Eveningness Questionnaire (rMEQ) -a 5-item measure of chronotype developed by Adan and Almirall (1991) Positive and Negative Affect Schedule (PANAS) -a 20-item measure including 10 items measuring positive affect and 10 items measuring negative affect (Watson et al., 1988).The scale is a measure of immediate emotions (e.g., hostility, excitedness) and was used in the current study in order to measure a change in immediate mood before and after CBM training.

Computational model
An updated version of an ALCOVE computational model of associative learning (24) was used to compute the primary outcome measure; learning rate.The model is fitted to trial-by-trial responses as detailed here.Briefly, the model uses a connectionist framework to model error-driven learning during the CBM task.The update to the model allows it to read in pre-training data to account for an individual's bias in judging overt and ambiguous happy and sad facial expressions (25).The model is parameterised to estimate a maximum effective learning rate ( effmax ), referring to the greatest speed along the morph continuum in which feedback is incorporated into new responses.Learning applied to new judgments depends on the position the facial stimulus on the morph continuum, resulting in an effective learning rate at each morph.The maximum effective learning rate ( effmax ) ranges from 0-1 where higher values represent a greater degree of the prediction error contributing to updating judgements of faces.The model also estimates generalisation ( ), the degree to which feedback from the prior trial is used to σ update responses to adjacent stimuli on the morph continuum.Here, the effective learning rate is adjusted to the training threshold ( effthr ) i.e., there is no maximum limit and it is centred around the facial morphs that the participant was receiving feedback on.Other parameters included: 1) inverse temperature ( ) (where higher θ values represent increased response reliability), 2) emotion bias (gH -gS) (ranging between -1 to 1 where positive values represent excess sad judgements on overt facial expressions), and 3) the pretraining indifference point (a model-based measure of the point at which participants distinguish between happy and sad faces, analogous to the balance point).

Exploratory analyses
In an exploratory analysis, the outcome measures were the post-training positive and post-training negative affect (subscales of PANAS score).The change in affect from pre to post training (paired t-test) was tested and 2x2 ANOVAs were performed to examine whether changes in affect after CBM training interact with chronotype group and synchrony condition.Finally, additional parameters derived from the computational model of associative learning are reported and interpreted including: gH -gS bias, inverse temperature ( ) and generalisation ( ).

Positive affect
Overall, there was strong evidence that 3 blocks of active CBM produced changes in participant positive affect decreasing from 30.0 (SD = 8.5) to 28.4 (SD = 9.0) (mean difference = 1.62, paired t-test t(173) = 5.52, p<.001).There was strong evidence for a main effect of group on post-training positive affect where late chronotypes (M = 26.49,SE = .92)had lower positive affect compared to early chronotypes (M = 30.60,SE = .97)(F(1,170) = 9.43, p = .002,η p 2 = .053).However, this effect disappeared when pre-training positive affect and sleep quality were added as covariates.There was no evidence for a main effect of condition or interaction effect.When participants that had recently taken stimulants were included in analyses, there was weak evidence for a main effect of condition where post-training positive affect was higher in the synchronous (M = 29.42,SE = .38)compared to asynchronous (M = 28.40,SE = .39)condition (F(1,201) = 3.5, p = .063,η p 2 = .017).

Negative affect
BMJ Publishing Group Limited (BMJ) disclaims all liability and responsibility arising from any reliance Supplemental material placed on this supplemental material which has been supplied by the author(s) . The reduced version is based on the full 19-item MEQ version and has good reliability, validity and re-test reliability.Total scores range from 4-26 where higher scores indicate increased morningness and cut-off scores indicate chronotype groups: late chronotype <12, neither chronotype 12-17, early chronotype >17.